Swift: NSRange vs Range <String.Index>

Swift: ExportStrings

func exportStrings() -> Void {
    var foo: String = ""
    var bar: String = ""
    
    if let result = result {
        let rangeFoo = result.rangeOfString("foo:")
        let rangeBar = result.rangeOfString("?bar=")
    
        if let rangeFoo = rangeFoo {
            if let rangeBar = rangeBar {
                let indexStartAddress = rangeFoo.endIndex
                let indexEndAddress = rangeBar.startIndex
                let indexStartAmount = rangeBar.endIndex
                let indexEndAmount = result.endIndex
    
                foo = result[Range<String.Index>(start: indexStartAddress, end: indexEndAddress)]
                bar = result[Range<String.Index>(start: indexStartAmount, end: indexEndAmount)]
            } else {
                foo = result[Range<String.Index>(start: rangeFoo.endIndex, end: result.endIndex)]
            }
        } else {
            return
        }
    }
}